Python script for copying podcasts/audiobooks to an MP3 player. This is useful for waterproof MP3 players like the Shokz OpenSwim that have limited controls. This will take any format, apply loudness normalization, split it into 5 minute chunks and copy it to the player as MP3. Requires ffmpeg and mp3splt.

swim_mp3.py

import argparse
from pathlib import Path
import tempfile
from subprocess import check_call

def main():
  parser = argparse.ArgumentParser()
  parser.add_argument("--input", type=Path, required=True)
  parser.add_argument("--media-dir", type=Path, default=Path("/run/media/your_user/your_device"))

  args = parser.parse_args()

  if not args.media_dir.is_dir():
    raise RuntimeError("Player not mounted.")

  out_dir = args.media_dir / args.input.stem.replace(".", "_")
  print(f"Writing to {out_dir}")

  with tempfile.TemporaryDirectory() as tmp_dir:
    normalized_file = Path(tmp_dir) / "normalized.mp3"

    check_call([
      "ffmpeg",
      "-i", str(args.input),
      "-filter:a", "speechnorm=e=6.25:r=0.00001:l=1",
      "-b:a", "192k",
      str(normalized_file),
    ])

    check_call([
      "mp3splt",
      str(normalized_file),
      "-t", "5.0",
       "-a",
       "-d", str(out_dir),
    ])

if __name__ == "__main__":
  main()